What is SAP HANA?
SAP HANA stands for High Performance Analytical Appliance- in-memory computing engine. HANA is linked to ERP systems; Frontend modeling studio can be used for replication server management and load control.
What are the different types of replication techniques?
The three types are as below:
- ETL based replication using BODS
- Trigger based replication using SLT
- Extractor based data acquisition using DXC
What is the role of the persistence layer in SAP HANA?
SAP HANA has an in-memory computing engine and access the data straightaway without any backup. To avoid the risk of losing data in case of hardware failure or power cutoff, persistence layer comes as a savior and stores all the data in the hard drive which is not volatile.
What are the two types of Relational Data stored in HANA?
The two types of relational data stored in HANA includes
- Row Store
- Column Store
What are the advantages and disadvantages of row-based tables?
Row based table advantages:
- The application needs to only process a single record at one time (many selects and/or updates of single records).
- The application typically needs to access a complete record (or row).
- Neither aggregations nor fast searching are required.
- The table has a small number of rows (e. g. configuration tables, system tables).
Row based table dis-advantages:
- In case of analytic applications where aggregation are used and fast search and processing is required. In row based tables all data in a row has to be read even though the requirement may be to access data from a few columns.
What are the advantages of column-based tables?
Column-based table Advantages:
Faster Data Access:
Only affected columns have to be read during the selection process of a query. Any of the columns can serve as an index.
Columnar data storage allows highly efficient compression because the majority of the columns contain only few distinct values (compared to number of rows).
Better parallel Processing:
In a column store, data is already vertically partitioned. This means that operations on different columns can easily be processed in parallel. If multiple columns need to be searched or aggregated, each of these operations can be assigned to a different processor core
Name various components of SAP HANA?
- SAP HANA DB
- SAP HANA Studio
- SAP HANA Appliance
- SAP HANA Application Cloud
What is SLT?
The full form of SLT is SAP Landscape Transformation which is nothing but a trigger based replication. It is the replication technology to pass the data from the source system to the target system. Here the source can be either SAP or non-SAP whereas the Target system is SAP HANA system which contains HANA database.
What are the advantage of SLT replication?
- SAP SLT works on trigger based approach; such approach has no measurable performance impact in the source system
- It offers filtering capability and transformation
- It enables real-time data replication, replicating only related data into HANA from non-SAP and SAP source systems
- It is fully integrated with HANA studios
- Replication from several source systems to one HANA system is allowed, also from one source system to multiple HANA systems is allowed.
Latency is the length of time to replicate data (a table entry) from the source system to the target system.
What is logging table?
A logging table in the source system that can record any changes to a table that is being replicated. This thereby ensures that SLT replication server can replicate these changes to the target system.
What is the role of master controller job in SAP HANA?
The job is arranged on demand and is responsible for
- Creating database triggers and logging table into the source system
- Creating Synonyms
- Writing new entries in admin tables in SLT server when a table is replicated/loaded
What are Transformation rules?
A rule specified in the Advanced Replication settings transaction for source tables such that data is transformed during the replication process. Example you can specify rule to
- Convert fields
- Fill empty fields
- Skip records
What is parallelization?
Column-based storage makes it easy to execute operations in parallel using multiple processor cores. In a column store data is already vertically partitioned means that operations on different columns can easily be processed in parallel. If multiple columns need to be searched or aggregated, each of these operations can be assigned to a different processor core. In addition, operations on one column can be parallelized by partitioning the column into multiple sections that can be processed by different processor cores (core 3 and 4 below).
What is ad hoc analysis?
In traditional data warehouses, such as SAP BW, a lot of pre-aggregation is done for quick results. That is the administrator (IT department) decides which information might be needed for analysis and prepares the result for the end users. This results in fast performance but the end user does not have flexibility.
The performance reduces dramatically if the user wants to do analysis on some data that is not already pre-aggregated. With SAP HANA and its speedy engine, no pre-aggregation is required. The user can perform any kind of operations in their reports and does not have to wait hours to get the data ready for analysis.
What is an Attribute?
Attribute represents the descriptive data used in modeling.
Example: City, Country, etc.
What is a Simple Attribute?
Simple attributes are individual analytical elements that are derived from the data foundation.
For example: Product_ID, Product_Name are attributes of a Product subject area.
What is a Calculated Attribute?
Calculated attributes are derived from one or more existing attributes or constants.
For example: deriving the full name of a customer (first name and last name), assigning a constant value to an attribute that can be used for arithmetic calculations.
What is a Private Attribute?
Private attributes used in an analytical view allow you to customize the behavior of an attribute for only that view.
For example: if you create an analytical view and you want a particular attribute to behave differently than it does in the attribute view to which it belongs, you can define it as a private attribute.
What is a Measure?
Measures are simple measurable analytical elements and are derived from Analytic and Calculation views.
What is a Simple Measure?
Simple Measure is a measurable analytical element that is derived from the data foundation.
What is a Calculated Measure?
Calculated Measures are defined based on a combination of data from OLAP cubes, arithmetic operators, constants, and functions.
What is a Restricted Measure?
Restricted measures are used to filter the value for an output field based on the user-defined rules
For example: you can restrict the revenue column only for Region = APJ, Year = 2013.
What is an Analytic view?
Analytic views are used to model data that includes measures. In case of multiple tables, measures must originate from only one of these tables (central table). You can model Columns, Calculated columns, Restricted columns, Variables and Input parameters.
What is Calculation view?
Calculation view is more advanced slice of the data and can include measures from multiple source of tables, can include advanced SQL logic. The data foundation of the calculation view can include any combination of tables, column views, attribute views and analytic views. We can create joins, unions, projections, and aggregation levels on the sources. You can model Attributes, Measures, Calculated measures, Counters, Hierarchies (created outside of the attribute view), Variables and Input parameters.
What is Hierarchy?
We create hierarchies between attributes to improve analysis by displaying attributes according to their defined relationships. There are two types of hierarchies:
Level Hierarchy: The root and child nodes are accessed only in the defined order. It consists of one or more levels of aggregation.
Example: We can drill down from Country to State and to City etc.
Parent/Child Hierarchy: This hierarchy contains a parent attribute and constructed from a single parent attribute.
Example: Employee master (employee and manager).
What are the factors that affect currency conversion?
Currency conversion is performed based on source currency, target currency, exchange rate, and date of conversion. You can select currency from the attribute data used in the view. Currency conversion is enabled for Analytic view and Calculation views.
What is the reason for the speed of HANA?
The information can be retrieved from Regular RDBMS technologies put the information on spinning plates of iron (hard disks). The information is stored in electronic memory, which is some 50x faster (depending on how you calculate). It stores a copy on magnetic disk, in case of power failure or the like. Also to add in, most SAP systems have the database on one system and a calculation engine on another, and the information is passed between them. With HANA, this all happens within the same machine.